Unit testing in Flutter passing BuildContext

One way is to use testWidgets in combination with a Builder widget:

testWidgets('me testing', (WidgetTester tester) async {  await tester.pumpWidget(    Builder(      builder: (BuildContext context) {        var actual = sut.myMethodName(context, ...);        expect(actual, something);        // The builder function must return a widget.        return Placeholder();      },    ),  );});

You can actually mock the BuildContext so the test will run headless. I think it's better but might be not a solution that you are looking for.

BuildContext is an abstract class therefore it cannot be instantiated. Any abstract class can be mocked by creating implementations of that class. If I take your example then the code will look like this:

class MockBuildContext extends Mock implements BuildContext {}void main() {   MyClass sut;   MockBuildContext _mockContext;   setUp(() {     sut = MyClass();     _mockContext = MockBuildContext();   });   test('me testing', () {   var actual = sut.myMethodName(_mockContext, ...);           expect(actual, something);  });}

Here is a simple way to retrieve a BuildContext instance inside a test case:

testWidgets('showDialog', (WidgetTester tester) async {  await tester.pumpWidget(MaterialApp(home: Material(child: Container())));  final BuildContext context = tester.element(find.byType(Container));  final dialog = showDialog(    context: context,    builder: (context) => AlertDialog(      content: Text('shown by showDialog'),    ),  );  // apply your tests to dialog or its contents here.});

This was inspired by Simple dialog control test from the Flutter test cases for the showDialog() function.

The whole "app" consist of a Container widget in a MaterialApp frame. The BuildContext instance is retrieved form by finding the Element instance related to the Container.